As shown in FIG. 1, in a multi-hop relay system, one or more Relay Stations (RSs) are set between Multi-hop Base Stations (MR-BSs) and Mobile Stations (MSs), so as to get extended coverage scope and expanded system capacity through relay transmission of signals of a base station and a terminal by the relay station. To meet the requirements of different application scenarios, the relay station may be set as a fixed relay station or a mobile relay station. Based on the situation whether prefixes and control messages are generated and transmitted, the relay station may be classified as a transparent relay station or a non-transparent relay station, and the former does not generate or transmit any prefix or control message. The multi-hop base station is called a base station for short hereinafter.
In a multi-hop relay network, a transmission link from a terminal to a base station via a relay station is composed of an access link and a relay link. Wherein, the access link is a communication link starting from or ending at the terminal, which may be either a link between the terminal and the base station that is directly connected with this terminal, or a link between the terminal and the relay station that is connected with this terminal. The relay link is a link between the base station and the relay station that is connected with this base station or a communication link between two relay stations. The relay station directly connected with the terminal is called an access relay station.
As to centralized scheduling, the base station allocates resources to the access link and the relay link of a multi-hop relay cell uniformly and generates a corresponding MAP (mapping message), or the relay station generates its own MAP according to indication information of the base station. As to distributed scheduling, the base station and the relay station respectively determine resource allocation to sub-relay station or the terminal and generate a corresponding MAP. The present invention can be applied to a non-transparent centralized scheduling multi-hop relay network.
In the case of a non-transparent relay station, the frame structure of the base station and that of the relay station respectively comprise an uplink subframe and a downlink subframe, and each uplink subframe and each downlink subframe are composed of an access zone and a relay zone respectively. Wherein, the access zone is used for access link transmission, and the relay zone is used for relay link transmission. A relay MAP refers to the MAP message sent by the base station or the relay station in the relay zone.
In the non-transparent centralized scheduling multi-hop relay network, a DCD (Downlink Channel Description)/UCD (Uplink Channel Description) broadcast message sent by the relay station via broadcast is generated by the base station. The base station sends the generated relay station broadcast message to the relay station at a primary management CID (connection ID) or a multicast management CID of the relay station, and the relay station reads MAC (Media Access Control) header information after receiving the message, finding that this message is a DCD/UCD message that is to be sent to a lower station, and then returns an acknowledgement header indicating that this message is well received. Every message is corresponding to one acknowledgement header. If the base station has not received the acknowledgement header when the timer is out, a management message should be sent again. Every time before sending this message down to the lower station periodically, the relay station sends a bandwidth request header to the base station to request for a downlink bandwidth, and the base station allocates a proper bandwidth to the relay station through a MAP IE, and then the relay station forwards the DCD/UCD within this bandwidth using a segmentable broadcast CID.
The existing technical scheme bears two disadvantages, one is that the bandwidth request header sent every time brings too large overhead, and the other is that it cannot be guaranteed that there is an available downlink bandwidth to be allocated to the relay station immediately after the base station has received the bandwidth request, and therefore bringing a long time delay.